Research On Suppressing Technologies Of Shunt Capacitors Switch Restrike

When a circuit breaker switches on high voltage shunt capacitors,high inrush current and overvoltage will occur and induce the restrike.The severe restrike harms the power system and some electrical devices.This paper studies the suppression technology towards the breaker restrike caused by capacitor switching.Based on the analysis of the mechanism of restrike caused by shunt capacitor switching,a precharge strategy for suppressing the switching inrush current is proposed.The target value of precharge is obtained by the theoretical derivation and the precharge strategy for single-phase,two-phase and three-phase precharge is put forward based on the target value.This paper build a PSCAD simulation model to validate the proposed precharge strategy and the parameters of the PSCAD model are obtained from the actual engineering.The simulation results show that the inrush current can be limited under 1.7p.u.The single-phase precharge can reduce the inrush current by 70%,and two-phase precharge can make the three-phase closing inrush surge rate reach over 50%.The duration time of closing transient is sharply shortened as well.Thereby the effectiveness of the proposed precharge strategy is validated.Based on the precharge target,a topology of precharge device is proposed.It can be used as a device to steadily output DC high voltage to precharge shunt capacitors.And a PSCAD simulation model is established to verify the validity of the topology.At last,according to the actual operation of shunt capacitors,the parameters of the precharge target value are modified to meet the requirements of engineering practice.Taking the closing time scatter of the vacuum circuit breaker into consideration,the effect of precharge strategy is simulated and verified,which shows that the proposed precharge strategy can suppress the inrush current well enough.